Surgical sensor

ABSTRACT

An integrated surgical anchor/localization sensor is disclosed. The anchor is adapted to be secured to an anatomical structure and contains a sensor housing. A receiver is located within the sensor housing and is adapted to sense reference signals generated by a surgical guidance system. A transmitter, connected to the receiver, conveys to a processor signals received by the receiver, so that the signals transmitted by the receiver are indicative of a current position of the anchor. Various other structures and methods are also disclosed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a surgical sensor which may beintegrated with an anatomical anchor. The sensor has particularapplicability in surgical procedures where it is desirable to track therelative movement of one or more structures.

[0003] 2. Description of the Related Art

[0004] Many surgical procedures are planned and guided using imagesobtained from imaging systems such as magnetic resonance imagers (MRIs),computer tomographic imagers (CTs), x-ray imagers, position emissiontomographic (PET) scanners, and photo-emission computer technology(SPECT). These systems permit physicians to obtain detailed preoperative(or intraoperative) views of anatomical structures using noninvasiveprocedures. Once these images are obtained, the physician typically usesthe images to plan a corrective surgical procedure. With the patientlying on an operating table, the images may be “registered” with thecorresponding physical space of the patient, and displayed on a screenin the operating room (OR). As the physician navigates probes or othermedical instruments within the patient, sensors on the instruments relaypositional information to a computer. The computer, in turn, overlays adisplay of the position of the instrument on the image of the anatomicalstructure. In this way, the physician may navigate through a surgicalprocedure by viewing a display screen in the OR. An example of a relatedart system is found in U.S. patent application Ser. No. 08/809,404,entitled: “Surgical Navigation System Including Reference andLocalization Frame,” and which is fully incorporated herein byreference.

[0005] Until now, the tracking of anatomical structures has been largelylimited to external tracking, either by taping a sensor to a patient'sskin, or by affixing an external clamp to the patient, such as aMayfield clamp, attached externally to a patient's head.

[0006] U.S. patent application Ser. No. 08/931,654 entitled BoneNavigation System which i is incorporated fully herein by referencediscloses a system which employs screws extending from a bone fragmentthrough a patient's skin and connected to a platform external to thepatient. Tracking elements such as, for example, emitters are located onthe platform so that when a bone fragment moves, so too does theplatform with the connected tracking elements. An array in the OR tracksmovement of the tracking elements, and this movement is correlated tothe movement of the bone fragment, in order to precisely track themovement of the bone fragment. Alternatively, clamps may be used, inplace of screws, to secure an array of tracking elements to a bonestructure. While such related art systems may generally be reliable,their structure is somewhat cumbersome, especially when the movement ofmultiple anatomical structures needs to be tracked. In addition, the useof the tracking elements and receiving array requires an unobstructedline of sight therebetween which not only limits implantation within apatient, but also can lead to interference.

[0007] For these reasons, in procedures such as those involving thespine or the reconstruction or repair of vertebral bodies, fracturedskulls, fragmented bones, or other damaged boney structures, it has beensomewhat difficult to track the relative movement of multiple anatomicalstructures.

SUMMARY OF THE INVENTION

[0008] It is an object of certain aspects of this invention to enablethe detection of anatomical structure movement during medical procedureswithout the use of cumbersome external equipment fixed to the patient.

[0009] It is another object of certain aspects of the invention toprovide a localization system for internal and/or external anatomicalstructures that do not require an unobstructed line of sight between apositional sensor and a detector.

[0010] It is a further object of certain aspects of this invention toprovide a localization system for internal anatomical structures whichmay be employed with minimal invasive procedures.

[0011] It is another object of certain aspects of this invention toprovide an integrated anchor and localization sensor that may bedeployed with relative ease.

[0012] It is yet another object of certain aspects of this invention toprovide an anatomical anchor which may serve as both a preprocedural andintraprocedural fiducial marker.

[0013] It is an additional object of certain aspects of this inventionto provide a reliable localization marker which may be placed in apatient in advance of a procedure and which may remain in the patientfor a period of time following the procedure.

[0014] It is a further object of certain aspects of the presentinvention to enable movement detection, with five or six degrees offreedom, of an anatomical structure or surgical instrument (whether theinstrument be an anchor, a catheter, or any other medical instrument).

[0015] These and other objects of the invention may be inherent orderived from the detailed description of the preferred embodiments.

[0016] The invention, in its broadest sense, may comprise one or more ofthe following aspects, either alone or in combination with one or moreadditional elements:

[0017] an anatomical anchor/sensor,

[0018] a receiver on an anchor for sensing signals generated external tothe anchor,

[0019] a transmitter on an anchor for conveying signals indicative ofthe anchor's location,

[0020] a signal generator on an anchor,

[0021] a connection for securing a receiver to an anatomical anchor,

[0022] a receiver and/or transmitter on a surgical screw, staple, pinrod, needle or soft tissue anchor,

[0023] an electromagnetic sensing coil on an anchor,

[0024] a magnet on an anchor,

[0025] an electromagnetic sensor having multiple collinear coils woundat differing angles, whether disposed on an anchor, a catheter, or othermedical instrument,

[0026] hard-wiring a transmitter on an anchor to a processor,

[0027] affixing a wireless transmitter to an anchor,

[0028] affixing a conductive electrode to an anatomical anchor,

[0029] a surgical screw having a hollow containing a sensor,

[0030] affixing a sensor to anchor using potting material,

[0031] a sensor housing for the head of a screw,

[0032] an attachable/detachable sensor mount for an anchor,

[0033] a grasping region for permitting medical personnel to screw aportion of a screw/sensor into an anatomical structure,

[0034] an integrated anatomical anchor/sensor where the sensor isdetachable,

[0035] methods and apparatuses for deploying an integratedanchor/sensor,

[0036] methods for making and using the above items,

[0037] procedures where the relative movement of instruments and/oranatomical structures are tracked and displayed, and

[0038] any other novel and unobvious aspects of the following disclosureand/or claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1A is an exploded view of an integrated sensor and bone screwin i accordance with one embodiment of the present invention;

[0040]FIG. 1B is an exploded view of an integrated sensor and bone screwin accordance with another embodiment of the present invention;

[0041]FIG. 2A is a schematic diagram of a single coil sensor inaccordance with the invention;

[0042]FIG. 2B is a schematic diagram of a dual-orthogonal coil sensor inaccordance with the invention;

[0043]FIG. 2C is a schematic diagram of a dual-coaxial coil sensor inaccordance with the invention;

[0044]FIG. 3 is a schematic diagram of a preferred system of theinvention and the environment of its use;

[0045]FIG. 4A is a perspective view of an embodiment of a driverassociated with deploying the integrated sensors of FIGS. 1A and 1B; and

[0046]FIG. 4B is a perspective of another embodiment of a driverassociated with deploying the integrated sensors of FIGS. 1A and 1B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] The invention will now be described in connection with theFigures wherein like parts are numbered with the same reference numeralsfor ease of discussion.

[0048] In accordance with the invention, there is provided an integratedsurgical anchor/localization sensor. An example of such an integratedunit is designated by reference number 12 in FIG. 1.

[0049] According to the invention, the anchor is configured to besecured to an anatomical structure. As illustrated in FIG. 1, an anchorin accordance with the invention may, by way of example, include asurgical screw 14. Screw 14 has a head portion 16, and a threadedportion 18. The threaded portion 18 is configured to be secured intoboney structure such as portions of long bones, vertebral bodies, theskull, or any other boney anatomical structure. In an preferredembodiment, the anchor may be a 2.2 mm cross-drive screw, 3-7 mm inlength. Preferably, the screw has keyed head portions 15 so that aconnector may be securely fastened to it. Screw 15 may also containslots 13 enabling the screw to be driven by various convention surgicalscrew drivers. It is also preferable for the screw 14 to be constructedof a material that will appear on an image scan and that will not causeinterference with the surgical guidance system in which it is intendedto be used. If an anchor is scanably detectable, it may alternatively beused as a fiducial marker. By way of example, when used withelectromagnetic guidance systems, the screw may be constructed ofaluminum.

[0050] While aspects of the invention are described herein in connectionwith surgical screws. the invention in its broadest sense is not solimited. Other anchors may be used in connection with the invention. Byway of example only, such other anchors may include surgical staples,pins, rods, soft tissue anchors such as pigtails, and headframe (e.g.,Mayfield) pins.

[0051] In accordance with the invention, there is also provided areceiver for sensing reference signals generated by a surgical guidancesystem. Such a system typically includes a reference signal generator 39as schematically depicted in FIG. 3. When an electromagnetic guidancesystem is to be used in connection with the invention, the receiver mayinclude at least one electromagnetic sensor 28 as schematically depictedin FIGS. 2A-2C. The invention is not limited to any specificlocalization guidance system or algorithm. Nevertheless, an example ofan acceptable system and algorithm may be found in U.S. Pat. No.5,592,939, entitled: “Method and System for Navigating a CatheterProbe,” and which is fully incorporated herein by reference.

[0052]FIG. 2A illustrates a sensor 28 having a single coil 20. Dependingon the specifics of the guidance system employed, such a sensor istypically capable of detecting position with either three or fivedegrees of freedom. In contrast, FIGS. 2B and 2C illustrate sensors 28having multiple coils capable of detecting position with up to sixdegrees of freedom. More particularly, the coil arrangement illustratedin FIG. 2B enables a reference signal to be detected with two orthogonalsensing coils 22. Alternatively, a plurality of collinear coils may beemployed. For example, in the coaxial arrangement illustrated in FIG.2C, two collinear sensing coils 24 are wound at differing or opposingangles. While any opposing angles will work, a preferred angle is 90°.In this manner, each coil will provide unique feedback in response tothe same reference signal generated by an electromagnetic guidancesystem.

[0053] The coil arrangement of FIG. 2C also has applicability inconnection with medical devices other than anchors. For example, thecollinear nature of the arrangement makes it particularly suitable fordevices that have working channels such as catheters where coils ofdiffering angles may be wrapped around the working channel to therebyminimize the size of the device.

[0054] The coil(s) of sensor 28 may be constructed of 40 AWG wirewrapped approximately 200 turns. Alternatively, the sensors may be 10μH-1000 μH surface-mounted inductors, preferably non-shielded. In analternative embodiment, a conductive localization system may beemployed. In this situation, sensor 28 may include a conductiveelectrode receiver. While the preferred electromagnetic system isdisclosed as including coil sensor, any electromagnetic sensor may beused including, but not limited to flux gates and reed switches.

[0055] The invention may also include a transmitter for conveying to aprocessor signals received by the receiver. In a preferred embodiment,the transmitter may simply include two wires 30 for hardwiring thesensor 28 to the electronics 32 of a surgical guidance system 34(schematically illustrated in FIG. 3). The transmitter wires 30 mayhave, at their distal ends (not shown) connectors for selectivelyconnecting them to the surgical guidance system 34. Preferably, thetransmitter wires 30 include two pair of 40 AWG twisted bifilar wire,with an outside diameter less than about 0.062 inches. It is alsopreferable that the transmitter wires be compatible with sterilizationprocesses so that they may be safely used within an anatomical body.

[0056] In an alternative embodiment, the transmitter may be wireless,transmitting signals to the surgical guidance system via radiofrequency, for example. In such an embodiment, a transmitting circuitand antenna may also be part of sensor 28. Since the details of wirelesstransmitter systems are known in the art, for brevity, they are notrepeated herein. Sensor 28 may further include a battery (not shown) forpowering the transmitter. Alternatively, a voltage may be provided tothe transmitter by induction using an external coil included as part ofsensor 28. Examples of such systems are described in concurrently filedapplication Ser. No. ______, entitled “Surgical Communication and PowerSystem” which is fully incorporated herein by reference.

[0057] As previously described, a sensor located on an anchor mayreceive signals from a signal generator external to the patient. Theinvention may, however, be embodied in a system with the reversearrangement—i.e., element 28 being a signal generator internal to thepatient and the sensor being located external to the patient. In thisscenario, and if the ii invention uses an-electromagnetic guidancesystem, the internal signal generator may, in its simplest form, be amagnet.

[0058] Also in accordance with the invention there may be provided aconnector for securing the receiver to the anchor, the connector beingconfigured so that the signals conveyed by the transmitter areindicative of a current position of the anchor. As embodied herein, andas illustrated in FIG. 1A, the connector may include housing 26 mountedto the head 16 of screw 14. Housing 26 may include wire relief groove 33for transmitter wires 30. Housing 26 may also include a keyed opening 27for receiving corresponding keyed screw head 16. This keyed arrangementprevents housing 26 from rotating on screw 14, thereby ensuring that thesensor 28 remains in a fixed position to provide an accurate reading ofthe position (i.e., location and/or orientation) of screw 14. Housing 26preferably has a plurality of flat grasping surfaces 31 enabling thescrew to be driven into a boney structure by manipulating the housing26. Housing 26 may be either detachable, fixedly secured to, orintegrally formed with screw 14, so long as it satisfies the function ofsecuring a sensor to the screw. To this end, housing 26 may contain anopening 29 opposite keyed opening 27, for receiving sensor 28. Ifhousing 26 is integrally formed with screw 14, slots 13 may beeliminated or alternatively located at the surface of opening 29.

[0059]FIG. 1B illustrates an arrangement similar to FIG. 1A, except thata threaded cap 17 screws onto threaded end 19 of housing 26, securinghead 16 of screw 14 to housing 26. With this arrangement, sensor housing26 may be selectively removed from screw 14.

[0060] Sensor 28 may be secured to housing 26 in any appropriate manner.For example, it may snap fit and/or be glued into opening 29.Alternatively, coils or other sensors may be deposited in opening 29 andthe opening thereafter filled with a suitable potting material, such assurgical cement. In its broadest sense, the connector of the inventionmay be any material or mechanism capable of joining the receiver to theanchor, ranging form a quantity of potting material to structures whichare molded, mechanically attached to, bonded to, or integrally formedwith the anchor.

[0061] In an alternative embodiment (not shown) screw 14 may have apartially hollowed construction in lieu of the housing 26, and thereceiver may be contained within the hollow. In such an embodiment, theconnector may be potting material for securing the receiver within thehollow or may include a cartridge for removably securing the sensor inthe hollow. In fact, removability of the sensor from the anchor may bebeneficially incorporated into mechanical linkages to provide thephysician with flexibility to attached and detach the sensor as thephysician sees fit.

[0062] While the anchor/sensor of the invention may be used as afiducial marker, it has particular advantage for use in tracking boneyanatomical structures such as vertebral bodies during spinal proceduresor bone fragments during reconstructive procedures. By way of example, aphysician may obtain an image of a fractured long bone using fluoroscopyor any other imaging device. Using a device such as cannulated driver 40(illustrated in FIGS. 4A and 4B), the physician may implant screw/sensorinto a boney structure. Specifically, driver 40 includes handle 42, neck44, and socket 46. Socket 46 includes opening 48 shaped to engagegrasping surfaces 31 of integrated screw/sensor 12. Driver 40 mayinclude a cannula or opening 50 extending therethrough to accommodatetransmitting wires 30. Alternatively, in lieu of opening 50, a slot 52(FIG. 4B) in an edge of socket 46 may be provided to permit wires 30 topass therethrough. In use, the physician loads a screw/sensor 12 intosocket 48, and passes the loaded socket through an incision adjacentboney structure in which the screw is to be secured. Using handle 42,the physician turns the screw, securing it to the boney structure.Thereafter, the physician removes the driver 40, pulling it over thetransmitting wires extended through opening 50 (FIG. 4A) or pulling theslot 52 (FIG. 46) away from wires 30

[0063] After screwing an anchor/sensor 12 into each of the bonefragments, the sensors are then registered with the image, such as in aknown mariner. With the scanned image appearing on a display device 36,the physician may manipulate the fractured bone fragments, trackingtheir movement in real-time. This is achievable because the surgicalnavigation circuitry 32, receiving signals from anchor/sensors 12 ineach fractured bone segment, can alter the image appearing on display 36to reflect a current position of the bone segments. For example, thescanned image may be digitized and correlated to sensors 28 so that asthe fractured portions of a bone are moved, simulated movement of thoseportions occur on display 36. In this way, a physician may preciselyreset a fractured bone. Related procedures are disclosed in pendingpatent application Ser. No. 08/809,404, entitled “Surgical NavigationSystem Including Reference Frame and Localization Fram,” and Ser. No.08/931,654, entitled “Bone Navigation System,” both of which are fullyincorporated herein by reference.

[0064] It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure andmethodology of the present invention without departing from the scope orspirit of the invention. In view of the foregoing, it is intended thatthe present invention cover modifications and variations of thisinvention provided they fall within the scope of the following claimsand their equivalents.

What is claimed is:
 1. An integrated surgical anchor/localizationsensor, comprising: an anchor adapted to be secured to an anatomicalstructure; a receiver, for sensing signals generated by a surgicalguidance system; a transmitter coupled to the receiver, for conveying toa processor signals received by the receiver; and a connector forsecuring at least the receiver to the anchor, the connector beingconfigured so that the signals conveyed by the transmitter areindicative of a current position of the anchor.
 2. An integratedsurgical anchor/localization sensor, wherein at least the receiver islocated in a cavity integral with the anchor.
 3. An integrated surgicalanchor/localization sensor, as set forth in claim 1, wherein the anchoris a surgical screw.
 4. An integrated surgical anchor/localizationsensor as set forth in claim 1, wherein the receiver includes at leastone electromagnetic sensor.
 5. An integrated surgicalanchor/localization sensor as set forth in claim 1, wherein the receiverincludes a plurality of collinear electromagnetic coils wound atdiffering angles.
 6. An integrated surgical anchor/localization sensoras set forth in claim 1, wherein the transmitter includes at least onewire connected to the receiver for hardwiring the receiver to theprocessor.
 7. An integrated surgical anchor/localization sensor as setforth in claim 1, wherein the transmitter is wireless.
 8. An integratedsurgical anchor/localization sensor as set forth in claim 1, wherein thereceiver includes a conductive electrode.
 9. An integrated surgicalanchor/localization sensor as set forth in claim 3, wherein the screwcontains an opening therein and where the connector includes pottingmaterial for securing at least the receiver within the opening.
 10. Anintegrated surgical anchor/localization sensor as set forth in claim 1,wherein the connector includes a housing that mounts on the anchor. 11.An integrated surgical anchor/localization sensor as set forth in claim1, wherein at least the receiver is selectively detachable from theanchor.
 12. An integrated surgical anchor/localization sensor,comprising: a threaded region; a grasping region for allowing at least aportion of the threaded region to be threaded into an anatomicalstructure; a sensor mounting portion; a receiver at least partiallycontained within the sensor mounting portion, the receiver configured tosense reference signals generated by a surgical guidance system; and atransmitter coupled to the receiver, for transmitting, as a function ofthe sensed reference signals, positional signals indicative of a currentposition of the receiver.
 13. The integrated surgical anchor/locationsensor of claim 12, wherein the sensor mounting portion is selectivelydetachable from the threaded region.
 14. The integrated surgicalanchor/location sensor of claim 12, wherein the transmitter includes awire for hardwiring the receiver to a surgical guidance system.
 15. Theintegrated surgical anchor/location sensor of claim 12, wherein thetransmitter is wireless.
 16. The integrated surgical anchor/locationsensor of claim 12, wherein the receiver includes at least oneelectromagnetic coil.
 17. The integrated surgical anchor/location sensorof claim 12, wherein the receiver includes a plurality of coilscoaxially arranged and wound at differing angles.
 18. The integratedsurgical anchor/location sensor of claim 12, wherein the receiverincludes a conductive electrode configured to receive conductivelocalization signals.
 19. A surgical localization sensor for integrationinto a tissue or bone anchor, the localization sensor comprising: areceiver for sensing reference signals generated by a surgicalnavigation system; a transmitter for conveying positional signals, as afunction of a current location of the receiver and the reference signalsgenerated by the surgical navigation system; and a connector formounting at least the receiver to the anchor, the connector configuredso that the positional signals conveyed by the transmitter reflect acurrent position of the anchor.
 20. The sensor of claim 19, wherein thereceiver includes at least one electromagnetic coil.
 21. The sensor ofclaim 19, wherein the receiver includes a plurality of electromagneticcoils coaxially arranged and wound at differing angles.
 22. The sensorof claim 19, wherein the receiver includes a conductive electrode. 23.The sensor of claim 19, wherein the transmitter includes a wire forhardwiring the sensor to a surgical localization system.
 24. The sensorof claim 19, wherein the transmitter is wireless.
 25. The sensor ofclaim 19, wherein the connector includes a housing configured to besecured to the anchor.
 26. An integrated surgical anchor/localizationsensor, comprising: an anchor adapted to be secured to an anatomicalstructure; a signal generator for emitting signals to be processed bysurgical navigation system circuitry; and a connector for securing thesignal generator to the anchor, the connector being configured so thatthe signals emitted by the signal generator are indicative of a currentposition of the anchor.
 27. The integrated surgical anchor/localizationsensor of claim 26, wherein the signal generator is an electromagneticfield generator.
 28. The integrated surgical anchor/localization sensorof claim 26, wherein the signal generator is a magnet.